US Army private Bradley Manning told a military tribunal on Thursday that he leaked secret files on the wars in Iraq and Afghanistan to WikiLeaks in order to start a "public debate."
Speaking in a firm and assured voice to read a nearly-hour-log statement, Manning said that when he deployed to Iraq he found himself alienated from his comrades and at odds with an army that "seemed not to value human life".
The 25-year-old, who is being held in military custody pending trial, said he would plead guilty to ten of the less serious of the 22 charges against him, but would deny aiding America's enemies, a crime which carries a life term.
Even if the court agrees to pursue only the lesser allegations, Manning still faces 20 years in military custody for leaking classified material to Australian activist Julian Assange's WikiLeaks whistle-blower website.
Reading a statement to the tribunal, Manning said he had initially attempted to contact traditional media outlets -- the Washington Post, the New York Times and Politico -- before deciding to pass the documents to WikiLeaks.
He sent the organization, which campaigns against government secrecy and publishes leaked information on a secure website, two military logs of daily incidents during the US campaigns in Iraq and Afghanistan.
"For me they represent the underground realities of the conflicts of Iraq and Afghanistan," Manning told the court.
"At the time I believed, and I still believe, these are two of the most significant documents of our time," he said, adding that he wanted to "spark a domestic public debate about our foreign policy and the war in general."
He also provided a vast trove of US diplomatic cables and cockpit video from a US helicopter gunship involved in an incident in which Iraqi civilians died.
Manning said he had chosen to work with WikiLeaks as it seemed to him, from what he had read, that the group "exposed illegal activities and corruption" and was "almost academic in nature."
But he said he never aimed to put US policy or US personnel in danger.
"I only wanted documents I was absolutely sure wouldn't cause harm to the United States," he insisted.
Manning presented himself during the nearly-hour-long statement as a young soldier interested in "geopolitical matters and information technology."
He said he had enlisted at age 20 "to get some real world experience and, under the GI bill, get some college opportunity."
-- Obsessed with killing --
"The more I tried to fit in at my work, the more I seemed to alienate my peers," Manning explained. The incident with the helicopter gunship, whose cockpit video he leaked, horrified him.
"We became obsessed with capturing and killing human targets," he said.
Manning also recounted an episode in which he was asked to look into the detention of 15 people by the Iraqi federal police.
When he determined that their crime had been to print critiques of corruption by the government of Iraqi Prime Minister Nuri al-Maliki, his superiors told him to drop the matter.
"I couldn't believe what I heard," he declared.
Manning's plea offer was presented to a military tribunal at Fort Meade in Maryland by his lawyer David Coombs, and the young soldier confirmed to the court that he understood the implications of his offer.
He intends to plead guilty to "unauthorized possession and willful transmission" of the video and of documents recounting civilian deaths during US operations Iraq and Afghanistan.
He will also admit "knowingly, intelligently and voluntarily" providing WikiLeaks with the classified diplomatic cables.
Judge Denise Lind asked Manning whether he understood the implications of his plea offer: "Do you understand this? Do you have questions about this? Do you still want to go forward with this?"
"Yes, your honor," he replied, before reading out a 35-page statement of his own attempting to outline his motivation in leaking the material.